The effect of spiral cold-bending manufacturing process on pipeline mechanical behavior

Abstract

Large-diameter steel pipes, fabricated through the spiral-welding manufacturing process, are extensively used in onshore pipelines for the transmission of energy (hydrocarbon) and water resources. However, their use in demanding applications, such as geohazard areas or in offshore applications has been very limited. Safeguarding the structural integrity in such areas of those pipes requires an efficient strain-based design framework. Bending deformation capacity in the presence of internal pressure is the major loading case under geohazard actions, whereas external pressure capacity governs the mechanical design in moderate-deep offshore applications. To predict accurately the structural performance of spiral-welded pipes, the coldbending manufacturing process should be taken into account. In the present paper, numerical models are developed simulating both the cold-bending process (decoiling and spiral bending) and the structural response of the pipe subjected to the loading conditions under consideration.The numerical modes have been verified against experimental results of spiral pipes conducted in the framework of a European research project. A parametric analysis is also conducted to examine the effect of spiral cold forming process on the structural behavior of spiral welded pipes. The results from the present study indicate that spiral-welded pipes can sustain significant amount of bending deformation and external pressure, in favor of their use in demanding onshore and moderately deep offshore pipeline applications.

Simulation and analysis of mechanical properties of cold-formed lock-seam of truss rods for on-orbit construction

“…Since the spiral cold forming process involves large bending deformation of the strip, and the diameter of the formed hollow rods is very small (40-100 mm) [35], so there are higher requirements on the plasticity and toughness of the material. Taking cold-rolled Q195 galvanized steel strip as the experimental object, the mechanical properties and chemical composition are shown in table 1.…”

Buckling of internally-pressurized spiral-welded steel pipes under bending

“…To account for material inelastic behavior, a von Mises plasticity model with isotropic hardening is considered. Furthermore, residual stresses are inserted in the finite element model as initial stresses before the application of bending loading, as calculated from a detailed simulation of the cold bending mechanism (including de-coiling process), which is presented in detail elsewhere [42], and is described briefly in the Appendix. Finally, before the application of internal pressure and bending loading, a hydrotesting loading step is performed corresponding to hydrotesting of the spiral-welded pipe in the pipe mill.…”

“…An extensive investigation on the influence of hydrotest on the structural response of spiral-welded pipes is presented in [42]. The results have shown that hydrotest reduces the residual stresses from the manufacturing process and, as a result, it affects pressurized bending response of the pipe.…”

“…It is also noted that the manufacturing process is associated with reverse plastic deformations, and therefore, an in-house cyclicplasticity constitutive model has been employed that accounts for both the plastic plateau and the Bauschinger effect of the steel material. For a more detailed presentation of the finite element simulation of spiral forming, as well as on the in-house plasticity model, the reader is referred to the paper by Chatzopoulou et al [42].…”